The present invention relates in general to cooperating coolant and oil flow path configurations for a diesel engine and the corresponding structural components which are required. Related to and comprising part of the present invention are the oil cooler configuration, the coolant manifold design in the block and the cooler cover which provides various flow paths for the oil. More specifically the present invention relates to the use of two separate oil coolers which are arranged with substantially parallel oil flow circuits with their corresponding flow outlet locations positioned near the front-to-rear center of the diesel engine block. An important part of the present invention is the cooperating configuration of the coolant flow cavity (i.e. manifold) which has a tapering design, front-to-rear, and provides balanced coolant delivery to all cylinders.
One of the important considerations in the design of a diesel engine is how to provide lubricating oil to the critical areas of the engine. A related consideration is how to direct and route the engine coolant to the engine cylinders. There is a relationship between the design of the oil cooler, the coolant flow path and the delivery of oil and coolant to various portions of the engine, such as the engine cylinders. The oil cooler may be placed at some location in the coolant flow loop in order to lower the temperature of the oil before delivery to the main oil rifle. Further, the coolant needs to be routed to critical areas of the engine in a way that provides efficient and balanced cooling. In particular, coolant delivery to the cylinders needs to be equalized in the sense of delivery and heat transfer so as to create a balanced and uniform cooling design whereby all of the cylinders are able to operate at substantially the same temperature.
Lubricating oil needs to be routed to engine areas such as the main bearings, rod bearings, piston cooling nozzles, valve trains, and camshaft gear train. The effectiveness of the lubricating oil depends in part on the oil temperature. In order to adequately address the heat transfer which occurs as the lubricating oil flows over and around these critical engine components, it is important to place an oil cooler in the lubricating oil flow loop. In one variation of a typical diesel engine arrangement, oil from the sump is first pumped to a full flow filter and from there to an inlet of the oil cooler. An alternative arrangement and one which is representative of that which is used with the present invention, routes the oil to the oil cooler and thereafter to the full flow oil filter. Typically a thermostat-controlled by-pass valve is positioned upstream from the inlet to the oil cooler and this valve is designed to route the oil around the oil cooler when the oil temperature is not high enough to require cooling (i.e., has not reached operating temperature).
Various arrangements of lubricating oil flow paths, oil filters and by-pass options are typically found in different diesel engine designs and different sized engines. However, the focus of the present invention is directed to a specific oil cooler design, its specific placement within the flow circuit, and the corresponding coolant delivery configuration. Therefore, a full explanation of the many variations for a range of diesel engine designs is not necessary. It is important to understand that the coolant delivery configuration, including the specific design of the coolant cavity, is an important aspect of the present invention.
In one typical type of lubricating oil flow circuit, the oil cooler is an elongated member which includes a series of closely stacked cooling fins with a continuous, single pass oil flow conduit extending therethrough. Lubricating oil from the oil sump (or full flow filter) enters the oil cooler at one end and traverses through the flow conduit to an opposite end outlet location. The oil cooler is typically positioned along the side of the engine block in a recessed cavity which cavity is in flow communication with the engine coolant. The cooling fins of the oil cooler are exposed directly to the engine coolant for effecting the required heat transfer and cooling of the lubricating oil. Another option for the oil cooler arrangement is to use a compact oil cooler design with the fins disposed toward the front end of the engine block. However, this design causes a higher horsepower draw and thus represents one type of parasitic loss.
In those designs where the oil cooler is elongated and extends for a majority of the block length, it has been discovered that there is a substantial pressure drop across the length of the oil cooler. This pressure drop is considered to be too great to be acceptable with the adverse consequence that it unnecessarily increases parasitic losses. A further fact learned about the elongated oil cooler version when combined with a typical coolant arrangement is that most of the heat transfer takes place in the very beginning section at the start of the flow path through the oil cooler.
In order to improve on coolant distribution to the engine cylinders and to decrease lubrication system and coolant system parasitic losses, the present invention was conceived. In the present invention, two oil coolers are used, and these two oil coolers are positioned end to end so as to generally simulate the physical configuration of an elongated oil cooler. An elongated coolant cavity is cast into the engine block with a front to rear tapering design along the lower surface. The flow of coolant is thereby made more uniform and balanced as it flows to each cylinder. The oil flow enters the front portion of the front cooler and in a parallel manner enters the-rear portion of the rear cooler. The flow passes through each oil cooler toward the middle of the engine and then to the oil filter head where the oil is filtered and then sent back across the engine in between the two oil coolers and to the main oil rifle. One advantage of this arrangement for the oil circuit is that the cooled oil comes in to the center of the main oil rifle and provides a more even distribution. Another advantage of the present invention involves the unique design of the tapered coolant flow manifold so that the flow of coolant to the oil coolers (flow over the fins) is relatively even and is able to provide more uniform and balanced cooling to the engine.
Two separate oil coolers have been used at least once in the K19 diesel engine design of Cummins Engine Company of Columbus, Ind. In the K19 engine configuration, the oil coolers are not elongated to extend end-to-end the full length of the block. There is therefore more of a restriction and greater parasitic losses as a consequence. Further, while the flow paths through these two K19 oil coolers are parallel, the flow entry is at the front end of each cooler with a flow exit (outlet) at the rear of each cooler. The entering flows are split and the exiting flows are combined. Of importance when considering this K19 design is the fact that in the K19 engine design, the exiting flows do not come out near the center of the block, but rather pass to the rear of the engine to connect with the main oil rifle. With front to back flow, the end cylinders have been found to run hotter than the front cylinders. Clearly, this K19 arrangement does not provide the more balanced and even distribution which is one of the advantages of the present invention. A further difference between the present invention and the K19 engine is the rearwardly tapered coolant cavity (i.e. manifold) and the resultant coolant flow paths to each cylinder. This design provides a more uniform and balanced flow of coolant to each cylinder.
In addition to the K19 engine arrangement there are various patent references which disclose a variety of cooler designs and cooling concepts. The following listed patent references are believed to provide a representative sampling of such earlier patented designs:
______________________________________ PATENT NO. PATENTEE ISSUE DATE ______________________________________ 1,310,251 Russell Jul. 15, 1919 1,931,935 Paugh Oct. 24, 1933 2,063,782 Barnes Dec. 8, 1936 2,525,191 Warrick et al. Oct. 10, 1950 2,623,612 Scheiterlein Dec. 30, 1952 4,041,697 Coffinberry et al. Aug. 16, 1977 Japanese Patent No. 4-103826 Apr. 6, 1992 ______________________________________